1. Field of the Invention
The present invention relates to valves. More specifically, the present invention is directed to a valve seal for producing a bi-directional fluid-tight and fire-safe seal on a valve sealing member.
2. Description of the Prior Art
Valves having a valve body and a valve sealing member rotatably mounted in a fluid passage therein are well-known in the art as is shown in the case of a so-called butterfly valve in U.S. Pat. No. 2,987,072. The provision for a separate resilient seal positioned in an annular groove of the wall defining the internal fluid passage of the valve body and encircling the valve sealing member or disc to engage a circumferential periphery of the valve disc and to create a seal thereby against fluid flow through the fluid passage when the valve disc is in its closed position is also shown in the aforesaid patent. Another example of a butterfly valve with a fluid pressure sealing ring or resilient member is shown in U.S. Pat. No. 3,771,763. Such prior art valve sealing members have generally not been adaptable to the provision of a metal-to-metal seal which is essential in providing a so-called "fire safe" valve as discussed in the July 17, 1978 edition of the "Oil and Gas Journal" in an article entitled "Fire Safe Valve Specs Summarized" by James Azzinaro. Some prior art attempts to provide a "fire safe" valve seal structure are shown in U.S. Pat. Nos. 3,986,699; 4,113,268; 4,130,285 and 4,162,782. Such prior art valve sealing mechanisms have significant inherent limitations such as either a failure to provide bi-directional "fire safe" sealing capability or a premature and rapid wear of the sealing face of the resilient element and the sealing edge of the valve disc which ultimately results in a fluid leak through the valve.
Accordingly, it would be desirable to provide a valve sealing structure which is adaptable for "fire safe" valve operations as well as other valve applications in a normal temperature environment while minimizing the effects of wear on the valve seal to avoid premature deterioration of the valve resulting in fluid leakage.